Pyrosulfuryl chlorofluoride process



United States Patent Office 3,245,753 Patented Apr. 12, 1966 3,245,753 PYROSULFURYL CHLOROFLUORIDE PROCESS Santad Kongpricha, Hamden, and William C. Preusse, Orange, Conn., assignors to Olin Mathieson Chemical Corporation, New Haven, Conn., a corporation of Virginia No Drawing. Filed Feb. 26, 1963, Ser. No. 261,192 3 Claims. (Cl. 23-14) This invention relates to an improved process for preparing pyrosulfuryl chlorofluoride (S O ClF).

Pyrosulfuryl chloride (S O Cl can undergo replacement reactions with various fluorinating agents to obtain pyrosulfuryl fluoride (8 1 and the aforementioned chlorofluoride. For instance, when 0 01 is reacted with antimony trifluorochloride, both chlorine atoms are replaced with fluorine atoms. When S O Cl is reacted with benzoyl fluoride, it has been found that a mixture of S O C1F and 5 0 1 is obtained. Neither fluorinating agent can be utilized to obtain the chlorofluoride as the sole reaction product since the predominant product is S O F It has been reported by En'gelbrecht in Z. anorg. allgem. Chem., 273, 267 (1953), that pyrosulfuryl chloride was reacted with AgF and AgF to obtain S O ClF as the sole product with no formation of S O F However, a yield of only about 30% was obtained, and since the silver salts are costly, their use in any commercially practical process would be prohibitively expensive. Furthermore, these silver salts are diflicult to handle since they are very susceptible to hydrolysis. In addition, the process disclosed in Engelbrecht, supra, is not suitable for adaptation to a continuous process since the formed S O ClF decomposes upon heating with excess amounts of silver fluorides.

S O C1F, because of the chlorine atom therein, is a more reactive intermediate than the analogous 0 1 It is useful as an intermediate in the preparation of various halosulfonates and sulfur oxyhalides. It is particularly useful in replacement reactions wherein derivatives of pyrosulfuryl mono-fluoride are obtained. However, as noted in the preceding discussion, the preparation of the chlorofluoride in good yield has not heretofore been possible.

Therefore, the primary object of this invention was to provide an improved process for the preparation of S O ClF. Another object was to provide a process for preparing S O ClF in good yield by the reaction of S O Cl with a fluorinating agent. Still another object of this invention was to provide an efficient process for the preparation of S O CIF wherein an inexpensive and readily available fluorinating agent could be utilized. Other objects will be apparent from the following discussion.

These objects have been accomplished in accordance with the present invention. It has been found that S O Cl can be reacted with fluorosulfonic acid, a strong fluorinating agent, to obtain pyrosulfuryl chlorofluoride in good yield. The S O ClF obtained as a result of this process is of high purity and is not contaminated with S O F No S O F is obtained even in the presence of a large excess of fluorosulfonic acid. This was an unexpected result since FSO H is considered a strong fluorinating agent, and it could be reasonably assumed that both chlorine atom-s in S O Cl would react similarly with fluorosulfonic acid. Therefore, a direct process is herein provided for the preparation of S O ClF wherein an inexpensive and readily available fluorinating agent is used. The process is also suitable for use in continuous operations since S O ClF is apparently stable in the presence of excess fluorosulfonic acid. The novel process of this invention is also characterized by the use of reactants which do not present any particular handling problems.

Briefly, the process described herein for the preparation of S O ClF comprises mixing S O Cl with fluorosulfonic acid and heating the resulting solution at a reaction temperature in the range of C. to 160 C. The preferred process embodiment utilizes a reaction temperature range of about to about 140 C. Since S O ClF boils at about 100 C. at atmospheric pressure, it is usually desirable to use a reflux condenser in the reaction system until reaction is complete and the pyrosulfuryl chlorofluoride can be distilled from the reaction mixture. However, the product can be removed from the reaction mixture as it is formed by using a distillation head and maintaining av proper reflux ratio, thus separating the product from the higher boiling reactants. It has been found that pyrosulfuryl chlorofluoride can be obtained by the process described herein in yields of up to 60% if distillation techniques are employed wherein all of the desired product is separated from higher boiling materials such as FSO H and S O Cl Although a molar excess of fluorosulfonic acid may be used in the process, there are no significant advantages to be derived from such use, and therefore in the preferred process embodiment equimolar amounts of S O Cl and FSO H are employed. However, it has been found that the product S O ClF is stable in the presence of excess fluorosulfonic acid (see Example 3 herein), and therefore this process can be used in the continuous production of pyrosulfuryl chlorofluoride if desired.

The following examples are offered as illustrative of the method of this invention. However, it is to be understood that these examples are not to be construed as limiting the scope of this invention.

Example 1 A 250 ml. round-bottom flask was equipped with a Water-cooled reflux condenser connected to a drying tube containing anhydrous calcium sulfate. Into the reaction flask was placed 21.2 g. (0.212 mole) of fluorosulfonic acid and 45.3 g. (0.212 mole) of pyrosulfuryl chloride. The solution was heated to boiling under reflux conditions for two hours. During this period, the flask temperature was about 120 to C.

After this refluxing period, the reaction mixture was distilled at atmospheric pressure and a liquid product boiling between 85 to 110 C. was obtained. This liquid was redi-stilled and 22.8 g. of a colorless liquid having a boiling point of 99 to 101 C. was collected. This boiling point corresponds to the value reported for pyrosulfuryl chlorofluoride by En-gelbrecht, supra. The following analytic-a1 data also revealed that the desired product had been obtained. Yield: 55%.

Analysis.Calcd. for S O ClF: Cl, 17.85. Found: C1, 17.82.

Infrared analysis showed the characteristic S-O absorption at 1250 and at 1500 cm.- and at 1210 and 1450 cm.- with respect to the SO Cl group. The S-F absorption was also found at 800, 810 and at 860 cmi Example 2 A 500 ml. round-bottom flask was equipped with an air cooled condenser connected at the top to a distillation head. Into the flask was placed 40.0 g. (0.40 mole) of fluorosulfonic acid and 43.0 g. (0.20 mole) of pyrosulfuryl chloride. The solution was heated under total reflux for 1% hours at a reaction temperature of about 130 to C. Then a liquid product boiling at 96 to 110 C. was collected upon distillation at atmospheric pressure. This material was fractionally redistilled, and

there was obtained an approximately 50% yield of colorless pyros-ulfuryl chlorofluoride boiling at 99 to 101 C.

Example 3 A 250 ml. round-bottom flask was equipped with a short air cooled packed column and a distillation head containing a water condenser. Into the flask was placed 49.5 g. (0.249 mole) of S O ClF and 57.4 g. (0.574 mole) of fluorosulfonic acid. The solution was heated to boiling under reflux conditions for a period of nine hours. The solution was fractionally distilled at atmosphcric pressure and no S O F (B.P. 52 C.) was obtained. Instead, the pyrosulfuryl chlorofluoride was recovered essentially unchanged.

What is claimed is:

-1. A process for providing pyrosulfuryl chlorofluoride which is essentially uncontaminated with pyrosulfuryl fluoride which comprises reacting pyrosulfuryl chloride with fiuorosulfonic acid at a temperature in the range of 100 to 160 C.

2. The process of claim 1 wherein a reaction temperature range of about to C. is utilized.

3. A process for providing pyros-ulfuryl chlorofluoride which is essentially uncontaminated with pyrosulfuryl fluoride which comprises reacting pyrosulfu-ryl chloride with a substantially equirnolar amount of fluorosulfonic acid at a reaction temperature of about 100 to about C. and distilling the pyrosulfuryl chlorofluoride product from the reaction mixture.

References Cited by the Examiner UNITED .STATES PATENTS 7/1951 McCann et al. 2314 X 4/1958 Muetterties 23-88 X 

1. A PROCESS FOR PROVIDING PYROSULFURYL CHLOROFLUORIDE WHICH IS ESSENTIALLY UNCONTAMINATED WITH PYROSULFURYL FLUORIDE WHICH COMPRISES A REACTING PYROSULFURYL CHLORIDE WITH FLUOROSULFONIC ACID AT A TEMPERATURE IN THE RANGE OF 100* TO 160*C. 